It is not clear what species he is referring to. In a 2nd edition he refers to this as Uca galapagensis but neither it nor the closely related U. herradurensis are found that far north. Given the description, the most likely species that it could be confused with found in the Gulf is U. zacae.

This is apparently an editing error, since he later states that he's replaced the name Uca macrodactylus with U. galapagensis.. Unfortunately, that species is not found in the Gulf, so the best guess is U. zacae.